I had heard once that the Isley Brothers were the group that had hit the US Top 100 pop music charts in the most different decades.
Wikipedia confirms that they did chart each decade from the 50's to the 2000's, starting in 1959 with "Shout!" and most recently in 2003 with "What Would You Do" (with numerous hits in the 60's, 70's, 80's and 90's). This seems tough to beat, but is this really the record? Or, more to the point, is it still the record? Are they also the group with the longest span from the first appearance on the charts to the last?